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Locks - Making Inland Waterways Navigable


Locks ~ Making Inland Waterways Navigable

The Panama Canal.  The Saint Lawrence Seaway.  The Mississippi River.  The Tennessee River.  The Ohio River.

What do all of these waterways have in common?  Locks.

Locks make it possible to traverse terrain that varies in elevation by raising or lowering the water levels depending on which direction a boat is traveling - upstream or downstream.

How critical are locks to inland waterways?

Consider the Mississippi River, which has headwaters that begin at Itasca Lake in Minnesota. At its start the Mississippi River:

  • Is a mere 20-30 feet wide
  • Is less than 3 feet deep
  • Is 2300 miles long (estimates vary as the river channel changes constantly)
  • Begins at 1,475 feet above sea level

More about the Mississippi:

  • Nearly half the river's elevation drop occurs within Minnesota
  • There are 29 locks beginning in Minneapolis with the St. Anthony Falls Locks
  • Its last lock is in St. Louis, Missouri
  • 670 miles of river exist between the first and last locks
  • The river drops 420 feet within this distance
  • Without locks, the river would not be navigable due to shallow areas and dangerous rock-filled rapids.

A Little Bit of Lock History

First used by the Chinese more than 2000 years ago, who invented the first lock system of two gates, canals have remained closely aligned with their original design.

The original two-gate design consisted of doors that went straight across the water which, due to water pushing against them, caused water to leak out between the doors.  

The current lock design was invented in 1480 by Leonardo daVinci, whose gates are still known today as Miter-V gates.  The gates meet in a shallow 'V' formation facing upstream, where water pressure pushes the gates together, forming a seal that is water-tight.  Most locks operate on gravity (water will seek its own level) using underground tunnels and flow valves for filling or emptying when opened or closed.

Lock Statistics

Here are a few statistics regarding the nation's locks:

  • There are more than 200 locks in the nation
  • Locks make navigation possible on 12,000 miles of inland waterways
  • Many of the locks are too small for today's barges
  • 50% of locks are more than 50 years old
  • 90% of locks and dams experienced service interruptions in 2009
  • 52 delays/service interruptions occur on average each day
  • Over 60,000 hours lost to unscheduled delays in 2013
  • Funding has been flat for nearly twenty years

Today, locks allow such river distances to be traveled by boats and barges, providing an economical way to transport commodities, such as grains and energy products, to various locations, including other cities, manufacturing plants, or ports for export.  

As part of the transportation system within the United States, continued operation of the locks is critical to affordable bulk cargo transport, especially for those commodities that are oversized or overweight.  In addition, fuel taxes generate funding: Barge transportation on the Upper Mississippi River Inland Waterways generated approximately $1.2 billion dollars in 2001.

The Trouble With Locks

Many of these locks are currently more than 50 years old (some are over 100 years old), have exceeded their useful life span, and are not adequate to handle the larger sized barges that are currently being built.  

In addition, many locks, such as the upper 3 most locks on the Mississippi, can only accommodate single wide barges, considerably increasing the cost and length of time for transport.

On the Tennessee River, the Chickamauga lock system is literally crumbling due to 'concrete growth' - an Alkali Aggregate Reation (AAR) that causes concrete to expand over time.  The expansion has caused mechanical failures and damaged the lock walls and gates until they are literally beginning to crumble.

Failing locks cause unscheduled delays or lock closures for repairs and maintenance, causing transportation on the river to halt indefinitely.  Since the 1990s, the rise in unscheduled delays has grown, and in today's society of just-in-time goods and materials delivery, this becomes a serious issue.  The global economy also increases the losses sustained when locks malfunction and unscheduled delays occur because the time to the intended port is extended.

Economic Impacts: At Home and In The Global Market

Barges compete and complement shipments made by train and truck, and in locations where inland waterways are available, they keep train charges for freight in check.  More significantly, lower prices afforded by barge transport help the nation compete in the global economy.  Any delay at a lock or within an inland waterway (e.g., water levels too low) reduces export availability, may cause freight re-routing which could damage or destroy perishables, limits competition, and increases costs.

Funding in Congress has remained mostly flat, although some funds were released at the end of FY2105 for work both on the Chickamauga Lock and another lock that has caused some of the most severe and extensive delays, the Olmsted Lock on the Ohio River.  Much of the funding is due to an increase in the barge fuel tax passed in 2014 by Congress, but it is not enough to address the many issues facing the aging lock system.

Aging Infrastructure

Like most of the nation's infrastructure, a comprehensive and innovative plan to upgrade and replace aging lock systems has been sorely neglected.  Here are a few other links regarding aging infrastructure and the urgent call to address these key components to the nation's economic viability, and its resilience to human-caused and natural disasters:

Kimberly Arsenault Kimberly Arsenault serves as an intern at the Cleveland/Bradley County Emergency Management Agency where she works on plan revisions and special projects. Previously, Kimberly spent 15 years in commercial and business aviation. Her positions included station manager at the former Midwest Express Airlines, as well as corporate flight attendant, inflight manager, and charter flight coordinator. Kimberly currently holds a master's degree in emergency and disaster management from American Public University.